CSV Library

Reading and Writing using the CSV library

Standard CSV Library

#Reading a CSV File
import csv
infile = open('1-1-1 sample.data','r') #the r means open for reading, use w when writing
reader = csv.reader(infile)
for line in reader:
    print(line)
infile.close()

['Field0', 'Field1', 'Field2', 'Field3']
['0', '1', '2', '3']
['text', '(also called strings)', 'can go', 'here too']
['pi', ' "e"', "Euler's constant", ' "e^(pi/2)"']
['3.14159', '2.71828', '0.577215', '0.207879576']
["You Can't", 'Have Your', 'Cake and', 'Eat it Too']

When Using quotes, you can use either singles (‘) or doubles (“) But if your text already includes one of them, use the other

'He turned to me and said, "Hello there"'

'He turned to me and said, "Hello there"'

Writing Data to a File

import csv

#Open the file for writing ('w')
outfile = open('1-1-1 newfile.csv', 'w')

#Construct a writer
out = csv.writer(outfile, lineterminator='\n')

out.writerow(['this','is','your','header'])
for i in range(10):
    #Write the rows using the writer
    out.writerow([i,i+1,i+2,i+3])

#Close the file
outfile.close()

#Note: The string used to terminate lines produced by the writer defaults
#to \r\n. This may cause issues for non-Windows users if you do not know this
#is the default.

## Creates a file with following contents:
this,is,your,header
0,1,2,3
1,2,3,4
2,3,4,5
3,4,5,6
4,5,6,7
5,6,7,8
6,7,8,9
7,8,9,10
8,9,10,11
9,10,11,12

Alternatively, most libraries contain a .to_csv() method you can use for exporting items to a csv or other tabular file

Revised example based on work first performed at ExploringDataScience.com